Cleaning compositions in shaped solid form have many advantages over other forms like liquid emulsion, gel or lotion forms. Most popular shaped solid forms are bars and tablets. Bars and tablets have the advantage over liquid or semi-solid forms in that they require minimal packaging and can be easily held by the consumer when applying the product on the desired substrate. However, shaped solid forms of cleaning compositions have to be carefully processed in order to give the desired shape stability during manufacture, transportation, storage and use by the consumer. The retention of the shape is important during the above stages between manufacture and use while ensuring that the rate of wear of the product during use is optimal. The shaped solid composition should abrade to the desired amount when applied by the consumer on the desired surface, while being long-lasting enough, so that the consumer is satisfied about the benefit derived to the cost paid for the product.
Shaped solid cleaning products have been conventionally made with insoluble soaps (stearates and palmitates) as the structuring agents to give the soap the desired shape while soluble soaps or synthetic surfactants provide the cleaning action. Many particulates e.g. starch or modified starch, inorganics particles like talc, calcite, clays (e.g. china clay) have also been incorporated in shaped solid cleaning compositions as structuring aids. Most of the above conventional agents added to shaped solid cleaning compositions perform one or the other function i.e. either cleaning or structuring, but not both. In fact, in most cases, they interact oppositely and it is often a struggle for a manufacturer to achieve both requirements in one go.
Certain highly absorbent materials like clay e.g. bentonite, attapulgite, kaolinite etc which are known to absorb oils have been used in cleaning compositions, but have had limited usefulness when incorporated in personal cleaning compositions.
Many researchers have tried to develop tailored materials to be incorporated in shaped solid cleaning compositions to provide various functionalities. Certain functionalised particulate materials have also been designed. Examples of design and synthesis of such particles are described in a review by Perro et al, J. Material Chem., 2005, 15, p3745-3760. One of the approaches used in the past is disclosed in U.S. Pat. No. 4,715,986 (Th. Goldschmidt AG, 1987) which describes particles for stabilizing or destabilizing emulsions of a size less than 100 microns, comprising fragments having on one side thereof hydrophilic group and on the other side thereof hydrophobic groups such that the hydrophilic and the hydrophobic groups are anisotropically distributed in a non-statistical manner. One of the methods for obtaining such fragments is by communition of hollow microspheres. In all the methods that are described heretofore, precursor materials have homogeneous distribution of surface groups, e.g. silica, alumina, hollow microspheres, microgel, carbon and starch.
The present inventors have been working in the area of such novel tailor-made materials and disclosed one such material in a co-pending Indian Patent application 668/MUM/2008. This patent application claims a particle with bipolar topospecific characteristics, whose precursor is an asymmetric 1:1 or 2:1:1 clay particle having alternating tetrahedral and octahedral sheets terminating with a tetrahedral sheet at one external surface plane and an octahedral sheet at another external surface plane, wherein a chemical group, having greater than 3 carbon atoms, and selected from an organyl or an organoheteryl group, is attached to coordinating cations on the exterior side of one of the surface sheets. The present inventors have worked on incorporation of a specific embodiment of this material in a shaped solid cleaning composition and with extensive experiments involving preparation of such compositions (especially bars) and optimising the resultant cleaning property and bar integrity arrived at the present invention.
In view of the limitations in the prior art, one of the objects of the present invention is to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.
Another object of the present invention is to provide a shaped solid cleaning composition which on the one hand has similar or superior properties compared to compositions prepared with conventional surfactants, having less of their disadvantages like low biodegradability, irritation to the skin and high cost.
Yet another object of the present invention is to provide for a shaped solid personal cleaning composition, which can be prepared using a simple and easy to scale-up process.
Yet another object of the present invention is to provide for a shaped solid personal cleaning composition that utilises a novel material which is an alternative to conventional surfactant and also has the functionality of a structurant thereby minimising the need for using high amounts of conventional structuring agents.